This invention relates to a gas furnace and, more particularly, to a gas furnace embodying a pulsating combustion principle.
Pulsating combustion heater systems have been known and are described in the prior art, See, for example, Hollowell U.S. Pat. No. 4,164,210 and Kitchen U.S. Pat. Nos. 2,916,032 and 4,309,977. Basically in such devices a combustible fuel and combustion air are admitted into a combustion chamber where they are ignited to produce an internal explosion, with resultant generation of heat. Immediately after each such explosion, an accoustically-produced negative pressure in the combustion chamber draws additional air and fuel into the combustion chamber through appropriate valves, whereupon the next explosion occurs and closes the valves until the next negative pressure occurs. Once started, a virtually self perpetuating series of heat releasing explosions are produced with combustion air and fuel being drawn automatically and intermittently through appropriate air and gas inlet valves as needed. In response to the combustion chamber pulses of high pressure, the hot exhaust gases from the combustion chamber are normally expelled forcefully through an exhaust pipe to an exhaust decoupling or expansion chamber from which an exhaust pipe or tail pipe extends to an exhaust flue outlet.
Room air to be heated may be passed by forced draft over the combustion system and then returned in heated condition to the room. To enhance the transfer of heat to the room air, external fins may be provided on the combustion chamber. Additional transfer of heat to the room air may be obtained by providing a heat exchange coil with fins on the tail pipe.
The internal explosions within the combustion chamber cause objectionable loud noise, particularly for a residential application. Various muffler arrangements have been proposed to attenuate the loud noise and consideration has also been given in the prior art to encasing the combustion chamber in sound insulating material that will assist in the absorbtion of the sound and vibration caused. For example, Kitchen U.S. Pat. No. 4,309,977 suggests supporting the combustion chamber of a pulsating combustion apparatus in a concrete casing.
An object of the present invention is to provide a pulsating type combustion air furnace with improved sound reduction means wherein the disadvantages and deficiencies in prior constructions are obviated.
Another object of the present invention is to provide a pulsating type combustion air furnace with sound reduction means comprising an exhaust decoupler body of sheet metal adapted to receive the pulsating gases from the combustion chamber, the exhaust decoupler body having a silencer tube therein with the lower end opening into the mid-region of said exhaust decoupler body and cooperating therewith to dissipate the energy of the pulsating exhaust gases.
A further object of the present invention is to provide an improved gas furnace of the pulsating combustion type having sound reduction means which include a resonator coupled to the exhaust pipe adjacent to the inlet of the exhaust pipe to the exhaust decoupler body for cancelling a portion of the energy of the pulsating exhaust gases before they can actuate the walls of the exhaust decoupler body to their resident frequency.
Still another object of the present invention is to provide a gas furnace of the pulsating type with sound reduction means which includes an air decoupler body enclosing the air valve of said gas furnace, such air decoupler body including a wall structure comprising an imperforate outer member, an intermediate sound insulating member and an inner perforated member, with the wall structure constructed and arranged to reduce the reverberation of sound within the air decoupler body and the escape of sound energy from the air inlet opening in the wall structure.
Other objects and advantages of the present invention will be made more apparent hereinafter.